Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$22.72	9.272%	$24.8266	$24.83	$24.85	$24.80
Purchase #2	$245.99	12.778%	$277.4226	$277.42	$277.40	$277.40
Purchase #3	$31.72	5.208%	$33.372	$33.37	$33.35	$33.40
Purchase #4	$144.65	8.652%	$157.1651	$157.17	$157.15	$157.20
Purchase #5	$35.61	4.309%	$37.1444	$37.14	$37.15	$37.10
Purchase #6	$35.51	10.464%	$39.2258	$39.23	$39.25	$39.20
Purchase #7	$247.72	3.499%	$256.3877	$256.39	$256.40	$256.40
7 purchase totals =	$763.92		$825.5442	$825.55	$825.55	$825.50